With compressors in general, and rotary compressors in particular, both the operating mechanism of the compressor and the motor for driving this operating mechanism are located within a sealed, hermetic casing. Because of this arrangement, some provision must be made for cooling of the motor or it will become damaged by overheating. One manner of doing this, generally accepted by the prior art, is to conduct the compressed refrigerant from the compressor chamber over the motor so as to provide cooling. However, generally, in the compression operation, the refrigerant is heated to such a point that it does not effectively cool the motor. Accordingly, to overcome this, liquid refrigerant from the condensation stage is frequently admixed with the compressed refrigerant before it is conducted over the motor.
Because of the high pressure on the discharge side of the compressor chamber and, particularly, the varying pressure within this chamber, care has to be taken as to the point of introducing or injecting this liquid refrigerant into the compressor. Care must also be taken that this liquid refrigerant is now carried over into the suction side of the compressor where it would decrease the efficiency of the compressor and thus its economy of operation.
One structure employed for the introduction of liquid refrigerant into the compressed refrigerant, for the purpose of cooling that compressed refrigerant, is shown in Rinehart, U.S. Pat. No. 3,109,297. According to that patent, a liquid discharge inlet 31 is located on the lower face of the compression chamber and, except for a portion of the cycle, that injection port is covered by the face of the roller which moves in an eccentric motion around the compression chamber. While this location of the injection port has frequently proven effective, it is so close to the vane which separates the high- and low-pressure sides of the compressor that there is great danger of the liquid refrigerant being carried over to the suction side of the compressor, thus diminishing its efficiency. In addition, the face of the compressor must be separately machined for each roller size, as the time of uncovering of the injection port is totally dependent upon the size of the roller.